1. The Invention
This invention relates to polymer formulation additives which impart a surprising reduction in smoke production to the plastic product upon combustion. In a further aspect, the invention relates to the use of dicyclopentadienyl iron and derivatives thereof, as smoke suppression additives in plastics. In a still further aspect, this invention relates to processes of increasing the smoke suppression properties of polyvinyl chloride plastics by the physical admixture of a small amount of dicyclopentadienyl iron, or derivatives thereof, and to the resulting polyvinyl chloride plastic having improved smoke suppression properties.
2. The Prior Art
Dicyclopentadienyl iron (ferrocene) has been used as a smoke reducing additive for hydrocarbon fuels -- see U.S. Pat. Nos. 3,294,685 and 3,341,311. This body of art is directed to the use of ferrocene and derivatives thereof, as a combustion catalyst to increase the quality of fuel combustion and, therefore, is directed to the increase of the overall flammability of the fuel.
Dicyclopentadienyl iron has also been employed as a flame retardant additive in polymers but in conjunction with chlorine and/or bromine containing compounds and, often, phosphorus and antimony containing compounds -- see Belgium Pat. No. 621,125, British Pat. No. 1,049,333 and U.S. Pat. No. 3,269,963. Although smoke reduction in polymers has been disclosed with other, unrelated additives -- see British Pat. No. 1,080,468 -- it is generally well-known that the use of flame retardant additives, e.g., ferrocene, in polymers, often leads to increased smoke production -- see papers by Einhorn and Gaskill in the University of Utah Polymer Conference (June 15-16, 1970), pages 29, 52.
The use of ferrocene as a plastics additive has been broadly suggested by the art for a number of purposes other than smoke suppression, for example, U.V. light stabilizing in polyvinyl chloride -- see J. Appl. Poly. Sci. 12(7), 1543 (1968); as an additive for improving corona resistance in plastics used as electrical insulating material, see British Pat. No. 1,200,739.
Now it has been discovered that polymer materials, especially polyvinyl chloride plastics, having reduced smoke generating properties, can be obtained by the simple physical addition of certain effective amounts of dicyclopentadienyl iron or derivatives thereof.